1. Field of the Invention
The present invention relates to a method of manufacturing a ceramic turbo charger rotor of a ball bearing support type in which an inner race of an angular ball bearing and a spacer are integrally secured to a journal portion of a metal shaft.
2. Related Art Statement
Generally, there is known a ceramic turbo charger rotor in which a ceramic turbine rotor and a metal compressor rotor are integrally connected by using a metal shaft. The known ceramic turbo charger rotor is installed in a bearing housing by means of a floating metal support or a ball bearing support.
In the known ceramic turbo charger rotor of the ball bearing support type, use is made of a ceramic turbo charger rotor having a structure such that the inner race of the angular ball bearing and the spacer are integrally secured to the journal portion of the metal shaft, which is used for connecting the ceramic turbine rotor and the metal compressor rotor.
The ceramic turbo charger rotor mentioned above is manufactured in the manner mentioned below. At first, a ceramic member having a wing portion and a shaft portion and a metal member having a journal portion, a compressor shaft portion and a bolt portion are prepared. Then, the ceramic member and the metal member are connected with each other to obtain a joint body, and the joint body is finished to obtain a ceramic-metal joint body. After that, the inner race of the angular ball bearing and the spacer are connected to the journal portion of the ceramic-metal joint body by means of a pressure-insertion method, and a rotation balance thereof is adjusted to obtain a ceramic turbo charger rotor shown in FIG. 2b.
The pressure-insertion operation is performed in the manner described in FIG. 4. As shown in FIG. 4, a tip portion of a ceramic wing portion 24 of a ceramic turbo charger rotor 23 is supported by a support member 22 arranged on a load cell 21. Under such a condition, an inner race 27 and a spacer 28 are pressure-inserted to a journal portion of a metal shaft 26 by using a pressure applying member 25.
Therefore, if an axis of the metal shaft 26 is inclined even slightly, a pressure-insertion condition of the inner race 27 and the spacer 28 is varied in response to an amount of inclination, and thus there often occurs a large deflection of more than 10 .mu.m during rotation (at the C portion of the metal shaft in FIG. 2b). In this case, prior to an installation of a compressor wheel, an amount of an adjustment of the ceramic turbo charger rotor shown in FIG. 2b becomes larger. Further, after the installation of the compressor wheel, it is necessary to perform a final balance adjustment such that portions of the compressor wheel and/or the nut are cut out. In this case, the compressor shaft, which is bent during the pressure-insertion operation, is stretched back to an original shape, and thus an unbalance amount of the ceramic turbo charger rotor shown in FIG. 2b is varied and increased. Therefore, under some circumstances, it is not possible to reduce a deflection amount during rotation within a predetermined range only by cutting out portions of the compressor wheel and/or the nut, and thus reliability as, for example, car parts is lowered.